A headmaster who failed to sack a child-molesting teacher says he will feel remorse "the rest of my days".

www.freeimages.com: datarec

The former headmaster of a Perth private school has told an inquiry he did not dismiss a teacher who was later convicted of sexually abusing five boys because he did not believe the man was a child molester.

The Royal Commission into Institutional Responses to Child Sexual Abuse is examining the prestigious school's response to allegations of inappropriate conduct by a teacher dating back to 1999.

The teacher, referred to as YJ, was jailed for five years in 2010 for sexually abusing five students.

The school and its staff cannot be identified.

The former headmaster told today's hearing that he considered sacking YJ after receiving a formal complaint about him in 2004 and discovering previous complaints dating back to 1999.

But while he believed the teacher's behaviour had been unprofessional, he did not think it demonstrated a sexual interest in children, nor did it justify dismissal.

.... I did not arrive at the conclusion that I had a child molester on my staff when it came to the welfare and safety of the children.

Former headmaster

"Whenever I re-read that series of letters, I was not convinced that there was anything being suggested that there was sexual activity, sexual interest in the children," he said.

"I arrived at the conclusion that there was inappropriate interest, that behaviour was unprofessional and unacceptable from that perspective, but I did not arrive at the conclusion that I had a child molester on my staff when it came to the welfare and safety of the children."

Headmaster saw 'no evidence' of sexual misconduct

The former headmaster told the inquiry that he now wished he had acted differently when concerns were first raised about YJ.

"I deeply regret that I did not conduct a more comprehensive investigation into the actions of [YJ] when the staff member first raised her concerns with me in 2004," he said.

"I failed to do this and it was an error of judgement on my part."

He said he laboured over whether to sack YJ, and his decision was not made casually.

"Rather, it was based on my conclusion that while [YJ's] actions were completely unprofessional," he said.

"I had no evidence suggesting that those actions amounted to sexual misconduct.

"Hindsight has shown my decision to be incorrect, and this is a remorse that I will carry for the rest of my days."

Teacher caressed boys' bottoms, inquiry hears

Earlier this week, the commission heard evidence from two former teachers who said the school did not take their concerns seriously enough when they reported YJ's behaviour.

They detailed many instances of inappropriate behaviour, including YJ caressing boys' bottoms and making students squat naked over wash basins while on a school camp.

One of the teachers wrote a lengthy letter detailing pages of incidents she and other teachers had witnessed, including YJ watching boys in the shower and touching them inappropriately.

The other was bullied by colleagues after raising concerns and felt her job was in jeopardy.

The commission has now wrapped up its public hearings in Perth.

It will continue in Canberra next month when two more witnesses, including the school's current headmaster, will give evidence.